What do you mean by "interchangeable"? If a function accepts a parameter of type impl Fn(...) -> ..., then this parameter can be either a function or a closure (so they are interchangeable). You can do many other other things with such types (return them, assign to variables, etc). IMO this is something that looks like 1st class functions.
What do you mean by "interchangeable"? If a function accepts a parameter of type
impl Fn(...) -> ..., then this parameter can be either a function or a closure (so they are interchangeable). You can do many other other things with such types (return them, assign to variables, etc). IMO this is something that looks like 1st class functions.See my comment above